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Bolts through Gear Mount - too short

DGlaeser

DGlaeser

Well Known Member
Drawing 34A calls out 6 bolts - AN4-12A's - which attach the landing gear mount to the spar. I started to install these today but the bolts don't protrude through the nuts - the end of the bolt is even with the end of the nut. The one on the bottom, closest to the wing bolts, has the added washer between the mount and the spar, so those threads probably don't even engage the fiber insert.

So obviously I'm wondering if anyone else has experienced this.
 
These "short" bolts is one of the most common things I find when inspecting RVs. And believe it or not, many people leave one of these bolts out altogether.
 
This is one of those things on the plans I would have hoped would have been changed by now. However, SOME of those holes will accept a "12" and be fine. Some will not. I was not at all comfortable with the 12s.
 
Thanks!

Thanks for the confirmation. As usual, right after I get some stuff from ACS something else pops up :rolleyes:

Mel - I'll double check to be sure I install all of them!
 
The one bolt that does not go through the wheel pant mounting bracket is shorter than the other 3. This is the one that often gets missed.
 
My guess is that the combination of powder coating thickness, and variations in prime coating or metal thickness all contribute to the seemingly short bolt callout.... if I had a comment it would be "... put a longer bolt in or thinner washer... ". Harshly put: use your head.... don't blindly follow the plans!

For what it is worth, John Schwaner in his text "SKY RANCH ENGIEERING MANUAL" states: ... "a properly torqued bolt will NOT loosen"... so I would worry less about how many threads show through the nylon on the nut and more about getting them all in and properly tightened....

cl
 
And "properly" torquing the bolts in question with the nut in the center of the spar section is a whole other topic. Personally, I just calibrated my arm.
 
vanplane said:
AC43.13 says one...and I think if all the threads are engaged by the nut when it's torqued, that extra out the back does no good at all. More danger in torquing the nut onto the bolt shank instead of the component.
Click to expand...

AC 43.13-1B calls for a MINIMUM of 1 thread. If you have the proper stack-up with 1-3 threads showing, you will not bottom out on the shank. If you have more than 3 threads, you need to go to a shorter bolt or add a washer.
 
13's

I asked Vans about this. Their reply was that is you get threads in the nylon then it okay. I went with 13's and used an extra washer to keep within 3 threads.

Mike
 
scard said:
And "properly" torquing the bolts in question with the nut in the center of the spar section is a whole other topic. Personally, I just calibrated my arm.
Click to expand...


These bolts are simple to torque. Just compute the run on torque for the bolt and add that to your torque value to determine final torque. The bottom bolts must be torqued from the bolt head but you can get a dog bone or crows foot on the top bolts.

Jekyll
 
Jekyll said:
These bolts are simple to torque. Just compute the run on torque for the bolt and add that to your torque value to determine final torque. The bottom bolts must be torqued from the bolt head but you can get a dog bone or crows foot on the top bolts.

Jekyll
Click to expand...

I think I read somewhere that when torquing from the head of the bolt is necessary that it is appropriate to lube the shank of the bolt (but NOT get lube on the threads). Is this correct?
Thanks.
 
Question: How does one "compute" he run of the bolt? Are you talking about figuring out what I've heard called the "friction value?" I have a "clicker" type (Craftsman, I think) torque wrench that begins at 25 ip (I think, maybe it's 20). I also have one of the -- I don't know what you call it -- style of wrenches with the dial, where the slashes are something like every 10 or 15 inch pounds apart, I'd guess.

Given that, how do I figure out what the friction value is to add that to the specified torque (after all the calculations for the contraptions I'm using just to get the torque (T,W,E, L ec) wrench on those bolts or nuts.

Up to now, I've just been torquing stuff to the high end of the chart.
 
Steve:

Per Circular AC 43.13-1B, there is no requirement to lube the bolt shank if torquing from the head. I don't think it would hurt as long as you ensure the threads remain clean and dry. You still must determine drag or run-on torque to be accurate. The lubed bolt may have less drag but it will be measurable.

Bob:

You've got yourself a dilemma that only the outflow of money can solve. The easiest method is to buy or borrow a small dial or pointer torque wrench that reads from 0-50 in/lbs. As you know, you can't measure 10 or 15 lbs of drag with a wrench that starts at 20 or 25 in/lb. I relied on a friend's cash outflow by borrowing his small pointer torque wrench for the duration of my build.

FYI:

I measured the run-on torque of all my gear mount bolts. I had values that spaned 7 to 20 in/lb on the -4s and 7 to 15 in/lbs on the -3s. These were all torqued from the head.

I torqued the 2 screws on the brace arms from the nut and they measured from 7 to 10 in/lbs.

For those that use the often heard rule-of-thumb of torquing to the center of the spread:
-3 range is 20-25, center value of 22 or 23.
-4 range is 50-70, center value of 60.

You can see from my measured run-on torques that arbitrarily torquing to the center of the range would result in many of the bolts being undertorqued with the worst example from my installation of a -3 being under severely torqued to only 8 in/lb.

Please don't take my measurements as indicative of all -3 and -4 bolts. Measure your own run-on torque each time you torque.

Jekyll
 
Got bolts? (yes!)

william weesner said:
i called vans on this one and got the "they're both in the kit" they were and i used them..thanks vans ;)
Click to expand...
I had them both also. They should make a note on the plans or in the instructions - but maybe they get lonely if no one calls with quesitons :rolleyes:
 
BO Bag

This was the bag that was on backorder forever. Who knows if you actually received the correct bolts in your bag. I would double check.

Darrell
 
Gear Mount Bolts too short-confirmation

"Drawing 34A calls out 6 bolts - AN4-12A's - which attach the landing gear mount to the spar. I started to install these today but the bolts don't protrude through the nuts - the end of the bolt is even with the end of the nut. The one on the bottom, closest to the wing bolts, has the added washer between the mount and the spar, so those threads probably don't even engage the fiber insert."

"So obviously I'm wondering if anyone else has experienced this."

This is a post from 5/21/06 from my fellow Michigander Dennis Glaeser.

Yes, I just experienced this problem and am going with -13 long bolts.

Jim
RV9A fuse
 
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